Grinding machine



May 6, 1947. s. E. WOODBURY GRINDING MACHINE 4 Sheets-Sheet 1 Filed Aug. 8, 1945 y 1947- s. E. WOODBURY 2,420,024

GRINDING MACHINE Filed Aug. 8, 1945 4 Sheets-Sheet 2 I .625 E i; W.

6/1 54 Fig.5. ggwm May 6, 194?. s E. WOODBURY GRINDING MACHINE Filed Aug. 8, 1945 4 Sheets-Sheet 5 M y 1947 s, E WOODBURY I GRINDING MACHINE Filed Aug. 8, 1945 4 Sheets-Sheet 4 TABLE Mummy MUTUR- L ll 5 with longitudinal ways in its upper face toward the rear and in these slides the elongated work table I8 carrying an adjustably mounted magnetic chuck I3 upon which the work to be ground by the wheel I2 is clamped.

Table traverse mechanism Longitudinal traverse of the work table l8 back and forth on the cross slide I! is effected through the medium of a transverse shaft 20, see Figs. 2 and 6, actuated either by connections to an individual motor, not shown, or by the hand wheel 2| which projects forwardly through the front wall of machine frame it] near its left hand side. In Fig. 6 the inner end of the shaft is shown as journalled in a gear reduction unit 22 interposed between it and its driving motor. It is provided with a fast toothed collar 23. Its outer end is suitably journalled in the front wall of the machine frame it]. The shaft carries a loose sleeve 24 formed integral at one end with a pinion 25 and at the other with a grooved ring in which rests a shipper segment 26. The sleeve 24 also has clutch teeth projecting from its opposite ends, those at the front being shown in Fig. 2 and those at the rear being shown in Fig. 6. The segment 26 extends outwardly and downwardly, see Fig. 2, being provided with a shank portion which is guided for transverse movement on a guide rod 21 disposed parallel to the shaft 20. This shank portion in turn has a pin and slot connection with the short inner arm 28 of a bell crank lever pivotally mounted to rock on a short shaft 29 projecting from the left side wall of the machine frame. The other and longer arm of the bell crank lever comprises a handle 36 located outside the wall of the frame. When the handle 30 is swung in one direction the sleeve 24 is shifted toward the right, as seen in Fig. 6, and is positively clutched to the shaft 20 through the collar 23. Under these conditions rotation of the shaft 23 to eifect the longitudinal traverse of the work table 18 is carried out by power from the motor. A latch 3| maintains this power connection until released by the operator. hand, when the handle 30 is swung in the opposite direction, the sleeve 24 is shifted toward the left, unclutched from the shaft 20 and clutched to the hub of the hand wheel 2|, whereupon longitudinal traverse can be effected as a manual operation.

The pinion 25, notwithstanding its shifting with the sleeve 24, always remains in mesh with a large gear 32 fast on a grooved transverse shaft 33 which is journalled in bearings provided in the front and rear walls of the machine frame 13. Splined on the shaft 33 is a collar 34 formed integral with a sprocket wheel 35. The collar 34 is embraced between the walls of a yoke 36 depending from the lower surface of the cross slide IT, as shown in Fig. 2 but omitted from Fig. 6. When the slide is given a cross feeding movement, as will be presently explained, the yoke 36 shifts the sprocket wheel longitudinally along the splined shaft 33 while operative connection b tween the two is at all times maintained.

A sprocket chain 3! runs about the sprocket wheel 35, upwardly over idler rolls 38, 38, in the slide l1 and thence in opposite directions to points of connection with the work table l8 adjacent its opposite ends and in its under face. It will be apparent, therefore, that rotation of the shaft 20 either manually or by power will, through the sprocket connections above described, impart a longitudinal traverse movement to the work table On the other 1 i 8 in a direction depending on the direction in which the said shaft 20 is rotated.

In the power operation of the machine, the length of work table movement and its points of reversal are determined by a pair of dogs 39 and 40 adjustably mounted in an undercut slot 4| provided in the front edge of the table i8, as shown in Fig. 1. To this end a sector 42 is mounted to rock on a horizontal axis with a shaft 43 projecting forwardly from the casing of a reversing switch 44 secured to one side of the cross slide [1, as shown in Fig. 3. The shaft 43 projects forwardly and is provided with a knurled operating head 45 at its forward end. A pin 46 projects forwardly from one corner of the sector into the path of the dog 39 and a pin 41 projects rearwardly from the other corner of the sector into the path of the dog 40. When either dog 33 or 40 rocks the sector 42 the switch 44 is thrown and the table operating motor is reversed and with it the direction of table movement. The reversing switch 44 has a snap action and it is so constructed and so connected with the sector 42, that it is not thrown until the sector is very near the end of its movement in each direction. Operation of the reversing switch may be effected manually by turning the operating head 45 at any time when the sector 42 is clear of the dogs 39 and 40.

At either end the table 18 carries a Wedge cam 8, one only being shown in Fig. 3, which cooperates with a safety switch 49 mounted at one side of the casing of the reversing switch 44. The switch 49 is normally closed and is opened by the depression of a roll-carrying plunger 50 standing the path of the wedge cams 48. Accordingly, if for any reason the table fails to reverse, one or the other of the cams 58 will depress the plunger 50, throw the switch 49 and stop the table motor, and preferably the entire machine, as will be presently explained. In the normal operation of the machine, of course, the table is reversed before the cams 48 reach the position of the plunger 53.

Cross feed mechanism The individual cross feed motor 5i is shown as attached to the right hand wall of the machine frame 16. It is connected through a pair of coupling collars 52, see Fig. 4, to a shaft 53 journalled in a bracket 54 mounted within the machine frame ID. The shaft 53 carries a worm 55 which is always in mesh with an elongated pinion 55 mounted on a transverse shaft 51 journalled in the upstanding legs of a yoke 58 within the enclosure of the frame I 0.

The elongated pinion 5G is always in mesh with a gear 59 fast on a shaft 60 which carries the cross feed lead screw 6| threaded into an elongatednut 62. The nut 62 is rotatably held in the front wall of the machine frame by means of a roller thrust bearing 63 and is connected to a hand wheel 64 projecting from front in convenient reach of the operator. At its inner end the shaft 53 is connected through ball thrust bearings 65 to a second yoke 66 projecting downwardly from the lower face of the cross slide I! at the right hand side of the yoke 36 already mentioned. This connection is the point of application of the cross feeding mechanism to the cross slide. In cross feeding in ither direction, movement is derived either from manual rotation of the hand wheel 54 and nut 62 or from power rotation in the nut 62 of the-screw 6|, through rot t on or the nut "62.

Preferably, the bearings longitudinal pressure can H meansof a threaded flanged bushing.

in the rearward direction, :if otherwise stopped, the cross reach its rearward limit of movement and therebearings 56, thus permitting of the shaft without damage that disclosed in my cro sslfeed mechanism e v These motors are shown diagrammatically t e main line switch 12. 1 current is carried. directly fit. interposed in the line is a switch 13.

to .the table traverse Iyvireslead to the tabletraverse motor through "thebefore mentioned table reversingswitclf 44.

e greater its connections with the shaft ESand the motor Means is provided for frictionally resisting the h V 7 As shown, there is a friction washer ilil interposed between the nut and theouter race of the a'djacentbearin'gfil 63 are so arranged that be applied theretoby The bushing n' aybe so adjusted as'to load the hearings to enable them to additionally resist turning of 'the'nut 61!, under normal rotation of the screw'Bl hyjpower transmittedfrom the motor 5|. How- "'eve'igjthe resistance offered by the washer fi'l and by bearings 163 is not so great as to interfere with "rotation of the'nut by means 64. direction, if the feeding of the handwheel Upon power cross feeding in the forward is not otherwise stopped,

thefgear' 58 will be brought into engagementwith :the'nut s2 an the nut will then turn in the bear-- 'in'gs fiii thus stopping the feeding and preventing damage to the machine. Under the condition last mentioned, the hand wheel 63 will turn idly, with the nut 52. Upon power cross feeding the feedingisfnot feed slide I! will upon frictional engagement between the shaft E l "and the nut 62 is increased'to such an extent nutwill turn with the shaft'in the roller continued rotation to the machine. In

that t this casealso the hand wheel 64 W111 turn idly with thenut' 62.

A" friction mechanism is provided for placing 'adrag on the shaft 53 in order to reduce the den y 'of'the shaft to "spin'and cause overfeeding when the motor 5l'is cut off. As shown inlifigg' i, the shaft 53 carries for this purpose'a friction disctB which runs between cylindrical friction members 59 and 1D yieldably and adjustably held together, and locked against rotation by "a'n'an'chor screw II threaded into the base of the bracket' fi l. The frictionon the disc 68 may be 'eujusteuso that the shaft W111 practically come to'a'dead stop the instant current is cut off from the motor 5]. However, by reducing the friction c-nthe disc'fiS to a limited extent, the momentum of the moving parts may be permitted to carry the shaft 53 a few turnsahea'd after current has been cut off from the motor!) I.

It will be understood that the general construe 'tion"of the machine heretofore described is no part of myinvention and is essentially the same as h before mentioned Letters f Patent No. 2,390,978,1out that the operation and control of its elements and the mechanism therefor now to be described is the subject matter of myinventi'on.

Wiring diagram and control switches I its already stated, the grinding wheel is driven h-y the spindle motor 13, the table is transversed o1" 'reciprocated by a motor not shown, and the is operated by the motor Fig. 11. Power is supplied and'beyond the switch 12 to the spindle motor table on-and-off in thewiring diagram,

13 one wire leads directly motor, and the other two Beyond the switch 7 opened and operation of'th'e i an be cl'ear "that feed motor 5l,'twof wires being 'thifoug'hga'f eed reverse s "main sw 'mentionedsafety switch 49, with the resultfthat 'theswitch being closed when uppermost position. The cam to the switch {switch'lBis a solenoid e'rgizedto cause the engagement of a friction rear leg of the yoke clutch 88-88.

the "p'eripheryandthe cam is symmetrical and ii'artesha'ped so'that rotatiaon in .6 I t with'theewitchesfilzand closedthe 'direction or rotation of the tablemotor can be r vers d by the operationof thefswit'ch '44 by means of the sector 42 in the manner already described. I

From the switch" current is conducted "to the connected'through 'a'feedmotor control Switch, the purposeor which will be more fully described. and one of the seine wires and anotherwire being connected itch T5, the purpose of which willalso be more fully described.

The main 11 'e'switch 12 is operated by asolein a control circuit which includes "a start an'd-stop switch I 11 which is,'or maybe, of fstandard construction and whichjismount'e'd onithe front of the machine, as shown in Fig. 1. The circuit of the solenoid "16 controlling the "itch also extends 'through'the before whenthe switch 48' is opened by one 'or the other ofthewedg'e earns 48, the main switcnwillbe entire machine will be stopped.

Thebperation of the feed motor is effected j'atone end, ortheoth'er end,"'or at bothends 'of 'the table l travel by me'ans of'a switch 18included in electrical'connection extending between two of the main circuit wires. The "switch 18 is preferably'a micro switch and it is mounted "on the cross feed slide adjacent the'roc'k'ing' seetor 42. Connected with the sector 42 to be moveme therewith is a cam 19, shown in Fig. 3, hav- "ing a flat bottom sidewhich is horizontal' wh'en the seotor'is in its mid position. The swit'chflii isprovi'ded with an upwardly biased plunger the plunger is inits 19 is so rented T8 thatthecam holds the swi'tch open when the sector 42 is in either of its extreme positions. However, when thesector "is moved back from either of'its extreme positions the plunger 88 rises and the switch 18 is'cl'os'ed,

thus starting the feed motor in the manner to be presently described.

Co 'neeted in the same control circuit withthe 81 which serves when enclutc h 88-88" the construction and function of 'whic'hwill be hereinafter fully described. ,Also [connected in the same circuit with the switch 18 and in parallel with the solenoid 81 is a solenoid 88 controlled by a space feed limit switch fiflwhich is preferably a micro-switch The solenoid'89 serves to'operate the before-mentioned feed motor control switch 14,

Space feed limit switch I The space feed limit switch 90 is carried by the 58, as shown in Fig. 6. It is normally closed and it has an upward profecting plunger 90 which serves to open the switch when it is'moved downward. For opening the j'swit'ch 90 after a predetermined amount of feeding has been effected, there is provided means movable in unison with an element of the feed mechanism. Preferably this means is a rotary cam, and I have shown a uniform motion cain 9i loos'ely mountedon the shaft 51 which carries the pinion 55. The camQl can be connected with the shaft to turn therewith, by means of the said The cam face is preferablyfat either direction from thPOSltlOfl shown'in' Figs: 6 and '7 will cause 7 it to engage the plunger 9|] to open the switch 90.

A suitable means is provided for restoring the cam 9| independently of the feed mechanism to its initial position after each movement. For this purpose there is shown a symmetrical cam 92 connected with but spaced from the cam 9|, this cam being also heart-shaped and being mounted with its point extending oppositely from that of cam 9|. The two cams 9| and 92 are normally held in the positions shown by means of a vertically movable weight 93 provided with a roller 94 which rides on the cam 92. The weight 93 is carried by a member 95 guided for vertical movement between the cam 92 and a collar on the shaft 51 and also guided by a vertical rod 9'! extending through a hole in a plate 98 carried by the casing of the switch 90. The cam 92 is preferably of the logarithmic type which has the advantage that the weight acts thereon with uniform rotative force irrespective of the position of the cam. When the shaft 51 is rotated with the clutch 88 engaged, the cams are moved in either direction out of the positions shown, but when they are released by the clutch the weight 93 acting on the cam 92 immediately returns both cams exactly to their normal positions. The exact normal positions are assured by the seating of the roller 94 in the notch in the cam 92.

As already stated, the cams 9| and 92 may be connected with the shaft 57 to rotate therewith by means of the clutch which comprises a friction disc 83 with an annular rim interposed between the cam 9| and a collar 88 fastened on the shaft 51 and having a conical rim. The friction disc constituting the loose member of the clutch can be engaged by means of an arm 99 which is horizontally pivoted at I and which can be swung to the left as viewed in Fig. 6 to move the cams endwise along the shaft and thereby exert clutching pressure betwen the friction disc 98 and the collar 88. The arm 99 is actuated by the before mentioned solenoid 87 when the solenoid is energized. A pin carried by the solenoid engages a rod IIlI to swing it upward about the axis of a horizontal shaft I02 to which the arm IDI is attached. The shaft I02 at its opposite end carries an upward projecting arm I03 which has pivotal connection with a lever I04 pivoted at its upper end to a link I05. A link I06 is pivotally connected with the lever I04 near the center thereof, this link being pivotally connected at its other end to the before-mentioned arm 99. It will be clear that through the mechanism shown, energization of the solenoid 81 will tend to move the arm 99 toward the left, as shown in Figs. 6 and 9. So long as the solenoid remains energized, the friction clutch 88 will remain engaged and the cams 9| and 92 will turn in unison with the shaft 51 and gear 56. Continued movement of the cam 9| will cause it to engage the plunger 90 to open the switch 90 which in turn causes the deenergization of the solenoid 89 and the opening of the switch 74, thus stopping the feed motor. The stopping of the feed motor stops rotation of the cam 9|, but the clutch 88 remains engaged and the cam cannot be returned to its initial position until the clutch is released by the opening of the switch I8 and the resultant deenergization of the solenoid 81.

In order that the space feed limit switch 90 may be used for varying amounts of feeding movement, provision is made for relative adjustment betwen the cam and the switch. Preferably the switch is bodily movable, and when there is a peripherally acting cam, such as 9|, the switch is adjustable toward and from the cam along a line which passes through the center of the plunger and the center of the cam 9|. Preferably the switch movement is vertical. When the switch is in its uppermost position it is barely held open by the cam 9| in its normal position, and the mounting and adjustment are such that a very slight downward movement of the switch permits the switch to be opened by movement of the cam through a very small angle. Further downward movement of the switch requires increased rotative movement of the cam to effect opening; and with the switch in its lowermost position, it will not be opened until the cam 9| has made nearly a half revolution. The switch 90 is secured to a member I01, which embraces the adjacent leg of the yoke 58 and is vertically slidable thereon. Vertical adjustment of the switch is effected by means of a rack I08 formed on a rod which projects upward from the switch casing and which meshes with a pinion I 09 on a shaft I I0 journalled in blocks I I I and II 2 supported on the legs of the yoke 58. The shaft H0 at its forward end carries a pinion H3, which meshes with a pinion II 4 on a shaft II 5, parallel with the shaft II 0 and journalled in the same blocks III and H2.

The shaft I I5 at its front end extends through a bushing II6 carrying at its front end a knob Ill and a graduated dial I I8, and the shaft is movable both rotatably and endwise with respect to the bushing. The bushing H6 is rotatable in a bearing II9 carrying a collar I20 with a mark thereon to cooperate with the graduations of the dial H8, the said bearing being secured to the front wall of the frame I0. The graduations 0f the dial II8 are preferably such as to represent thousandths of an inch of feeding. Rotative movement of the knob Ill and of the bushing H6 is transmitted to the shaft II5 by means of two arms I22 and I23 secured respectively to the bushing and to the shaft. These arms are connected by means of a pin I 24 which transmits rotative motion while permitting the shaft H5 and the arm I23 to move endwise. The pinions H3 and II 4 are of sufficient width to remain in mesh notwithstanding the endwise movement of the shaft H5 and the pinion H4.

The shaft I I5 can be manually moved endwise by means of a knob I25 at the front end thereof and this endwise movement of the shaft H5 is utilized to change the position of the feed reversing switch 15 as shown in Fig. 9. A collar IE6 is loosely mounted on the shaft II5 between two other collars fast thereto. The collar I28 has an upstanding portion which embraces the shaft IIO to prevent rotation, and it has a depending portion which engages the reversing switch to operate it. When the knob I25 and the various parts movable thereby are in their forward positions, cross feeding is effected in the inward direction, and when the knob I 25 and the said parts are in their rearward positions, cross feeding is effected in the outward direction.

From the foregoing description the operation of the cross feed control mechanism will be readily apparent. As already explained, the sector switch 18 is permitted to close as soon as the cam 19 starts to move with the sector 42 and the switch remains closed during substantially the entire time of movement of the sector from one extreme position to the other.

The space feed limit switch 90 is normally closed and the closing of the switch I8 energizes the solenoid 89 to-close the feed motor switch [4 and start. the operation of the feed, motor 5|. The feed motor, acting through the mechanism which has been fully described, causes feeding in the inward direction or in the outward direction according to the position of the feed reverse switch 15.

The closing of the circuit through the sector switch 18 simultaneously energizes the solenoid @1- which serves through the medium of the mechanism described to effect the engagement of the clutch 8B and to cause the cam iii to rotate in one direction or the other, according to the direction of feeding. Feeding will continue until the: cam 91 engages the plunger w of the switch 90. to open the switch and stop the feed motor. The cam 9| is symmetrical and its action is therefore the same, irrespective of the direction of rotation. The opening of the switch 59' deenergizes the solenoid 89 and opens the switch 14, thus'stopping'the feed motor. Over-running of the motor and connected parts is prevented or limited by. the friction disc 58 in the manner already described.

Notwithstanding the stopping offeeding the solenoid 81 remains energized until the sector 42 completes its rocking movement, whereupon. the sector switch 18, isagain opened, thus deenergizing the solenoid- 81- and releasing the pressure on the clutch 88-. Then; the. weight 93, acting on the. heart-shaped camv 92 returns both cams to. their; initial positions. The cam 92 issymmetrical, and the action istherefore the same, irrespective ofthe direction of rotation.

Bymertically adjusting the switch 96. by means I of the knob- I H, as already described, the switch can be so. placedthat it is opened after any desired amount of; angular movement ofthe cam 9 As already stated, the cam 9;l.is of such design that therise is. exactly proportionate tothe angular, movement. It therefore; follows that the amount ofangular movement prior to the-open-' ingot the switch 90 is exactly proportionate to theamountof;vertica1 adjustment of the switch. Thus. the amount of. feeding can be accurately controlled-by means-of the 'knob l i'lwith its grad-- uated dial MB.

It will be observed that feeding would be stoppediby, the reopening of the switch 18 upon completion of. movement of the-cam 19 to its op positeposition, even-though the cam-9l had not yet-openedthe-switch 95!, as the opening of the switch 18 would deenergizethe solenoids 81 and 8.5,. It: has-been found, however, that even with high table speeds the cam 91 operatesto open the; switch 95), before: the cam I9 reopens the switch-I8;

It has been stated that the sector switch 78 is electrically connected bietweentwo-of the main circuitwires, Preferably this connection is through the, reversing switch. 44 and also through endifeedswitch l21, shown diagrammatically,

in. Fig l1 and-indetail in;Fig; 10. When: the

switch-18 is: so connected; the reversing switch has two supplemental. stationary contacts- IN. and l29which are adapted to be engaged by a movable contact of l the; switch so that current is supplied to one; or the other of them according.

tothe position of;thc switch. So. far as the'con-v tacts. l 28- and [28 are concerned, the eswitch 1.44

may; be regarded as having twoseparateclosed. hastwo contacts I38):

positions, The"- switchi2] and; l-3.|. which areelectrically connected respec- V Y; h hercontactslflfi and [2,905 the reversing switch, 44. The switch LET has a. movable.

contact member I32 which is electrically connected with the switch 18 and which can be moved to engage the contact I3t, as shown in Fig. 11, or can be moved to the left to engage the con tact I31 or can be moved to an intermediate posi tion in which it engages both of the contacts I and HI. The switch is manually operable by a rock shaft 33 extending to the front of the machine, and having at its front end a handle or finger piece :34 by which it may be turned. At its rear end, as shown in Fig. 10, the shaft I33 carries an eccentric E35 fitted between two upright elements on the movable contact member of the switch. When the shaft is rocked by means of the finger piece 634 at the front end of the shaft $33, the eccentric l-35 is turned to move the contact member l32to any one of its-three described positions.

Inorder that the function and operation of the end feed switch I21- may be more clearly understood, letit be assumed that the table reversing switch 44: serves when in its left hand position, to cause movement of the'table toward the left, and serves when in its right hand position to cause movement of the table toward the right. It has already been pointed out that the switch 18- is cpen whenv the sector. 42 and the cam 19- are inone. or'the other of the tilted positions towhich they are-moved bythedogs39- and 40-, but isclosed while the sector and cam. are moving from one tilted positionto the other.

Let it be first assumed that the reversing switch is in its left hand position, and that the table is moving toward the left. The sector 4'2 and the cam 18 art tilted toward the right, as shown in- Figs; 1. and S; and are ready t'o-bemoved 'tcward the-left by thedog 39-. Under theas'sumed conditions, the contact I Z-Bof' the switch M and the contact |39 of the switch I 21 are alive, and current will fiow'through-th'e switch-Itasscon as this switch is closed" by movement of the cam lfltoward the left. Current will continue to flow until the cam 19, actuated Icy-the sector 42 and the dog 39, reaches-its-opposite tilted position to again open the switch 18, at which instant the reversing swic'h' M is snapped to'the right,.thus reversing the table. The closing of the switch l8 starts the feeding as already explained, and thus'feedingwill.be startedjust prior to the end of table. movementv toward the left. Feeding is stopped by'thecam 9i and the switch 90, as already explained,

The I reversing" switch is snapped to I the right at or'about the'instant that the switch 18-is reopened'by the-movement ofthe cam l9 toward the left, and thereuponthe. movable contact of the reversing. switch-disengages the supplementary contact I28 and engages the supplementary contact 128. This serves to :openthe connection to the switchicontact lflfl-and toclose the connection tothe switch contact I34. The table will nowmovev toward. the right, the switch 18- being held open by the. cam/l9,- which isnow in the position opposite to that-.shownin Fig. 3.. When the ce-misnext tiltedtowardthe right by the dog tii, the switch lit-is again closed, but no current flows therethrough .for the reasonv that the connection to the contact I30" has been broken, and. therefore. nowfeedingytakes place. From the descriptiongiven. it willbe clear. that feedingoccursjust before. the. end f. each left movement of the table, but that no feedin 5 r n a the end. of each .rightmovement of. the table N g} It will be obvious, without further detailed expianation, that the. above. described condition can be reversed by moving the switch member I 32 to disengage the contact I30 and to engage the contact I3I. Feeding then occurs just before the end of each right movement of the table, but no feeding occurs at or near the end of each left movement. Feeding can be effected just be fore each end of the table movement by placing the switch member I32 in its intermediate position in which it engages both of the contacts I30 and I3l.

As already stated, the construction embodying the present information is in many respects similar to that disclosed in my prior Patent No. 2,390,978. Cross feeding takes place during the interval of table reversal and with the work out of en agement with the wheel. There is usually available for feeding purposes an interval corresponding to about twice three-quarters of an inch of table travel. When all of the feeding is done within this interval, the grinding wheel cuts a new path over the entire length of the work. Without this arrangement the work returns to the wheel along the path already cut and grinding does not start until the work is carried over by the feed of the cross slide perhaps several inches from the leading end of the work. Also when the work approaches the end of its travel the metal that was left during prior reciprocation has to be ground away as an extra amount which is obviously objectionable.

The machine embodying the present invention retains all of the advantages incident to the invention disclosed in the said patent and it will be apparent that the adiustment of the extent of cross feeding can be changed by means of the knob II! as often and as much as desired in perfect safety while the grinder is running. When hand feeding is desired, this can be readily effected by means of the hand wheel 64 which can be used at any time without giving thought to the automatic cross feed mechanism. With the construction shown in the aforesaid prior application the amount of feeding was controlled entirely by a sector switch, such as the sector switch I8 of the present application, the amount of feeding being adjusted by moving the switch upward or downward so that it would be permitted by the sector cam to remain closed for a greater or less period of time. This may be referred to as a time anticipative feed. The construction shown in my prior patent is highly meritorious but the present construction has certain additiOnal advantages. One such advantage is that the limitation of feeding is effected directly by a mechanical means, such as the cam BI, which moves in unison of an element of the feed mechanism This may be referred to as space anticipative feed, and it places a more definite and certain limitation on the amount of feeding than can be effected by means of a sector switch, such as 78, wherein the time of current flow is to some extent affected by other factors such as the speed of table movement.

A further advantage in the present construction is that the feed is always definitely stopped by the feed mechanism itself without the necessity for depending upon the re-opening of the sector switch, In the prior construction. if the sector should be moved accidently or otherwise to its intermediate position, the sector switch would remain closed and cross feedin would continue indefinitely or until stopped by some additional mechanism specially provided for that purpose.

Having thus disclosed my invention and described in detail a specific embodiment thereof for purposes of illustration, I claim as new and desire to secure by Letters Patent:

1. In a grinding machine of the class described, the combination of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a control circuit for the motor having a switch therein which is open during the major portion of the table movement, means for closing 1e switch near the end of table movement in one direction to thereby start the motor and for opening the switch after a short predetermined interval, a second normally closed switch in the said control circuit, and means operated by movement of the feed mechanism for opening the second switch after a predetermined amount of feeding to stop the feed motor while the first switch remains closed.

2. In a grinding machine of the class described, the combination of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a control circuit for the motor having a switch therein which is open during the major portion of the table movement, a rocking sector operable by the table for reversing the table movement, means operated by the sector for closing the switch at the beginning of each sector movement to thereby start the motor and for opening the switch at the end of each sector movement, a second normally closed switch in the said control circuit, and means operated by movement of the feed mechanism for opening the second switch after a predetermined amount of feeding to stop the feed motor while the first switch remains closed.

3. In a grinding machine, the combination of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a control circuit for the motor having a switch therein which is open durng the major portion of the table movement, means operated by the table for closing the switch shortly before the end of table movement in one direction to thereby start the motor, a second normally closed switch in the said control circuit, a cam advanced by the feed mechanism from a predetermined initial position for opening the second switch to stop the feed motor after a predetermined amount of feeding, means for automatically returning the cam to its initial position regardless of the point to which it has been advanced, and manually operable means for varying the amount of feeding prior to the opening of the second switch.

4. In a grinding machine, the combination of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a control circuit for the motor having a switch therein which is open during the major portion of the table movement, means operated by the table for closing the switch shortly before the end of table movement in one direction to thereby start the motor, a second normally closed switch in the said control circuit, a cam movable in unison with the feed mechanism for opening the second switch to stop the feed motor after a predetermined amount of cam movement, and means for changing the relationship between the cam and opening the second switch to stop the feed motor after a predetermined amount of cam movement, a rack and pinion mechanism for moving the second switch relatively to the cam to vary the said predetermined amount of cam movement prior to the opening of the switch, and a device at the front of the machine for rotating the pinion to move the switch.

12. The combination in a grinding machine, of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a re versing switch for the motor, a control circuit for the motor having a switch therein which is open during the major portion of the table movement, means operated by the table for closing the switch shortly before the end of table movement in one direction to thereby start the motor, a second normally closed switch in the said control circuit, a cam movable in unison with the feed mechanism for opening the second switch to stop the feed motor after predetermined amount of cam movement, means including a manually rotatable knob at the front of the machine for moving the second switch toward and from the cam to vary the said predetermined amount of cam movement prior to the opening of the switch, and means for operating the reversing switch including a rod manually movable longitudinally and extending through the aforesaid rotatable knob.

13. The combination in a grinding machine, of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a reversing switch for the motor, a control circuit for the motor having a switch therein which is open during the major portion of the table move ment, means operated by the table for closing the switch shortly before the end of table movement in one direction to thereby start the motor, a second normally closed switch in the said control circuit, a cam movable in unison with the feed mechanism for opening the second switch to stop the feed motor after a predetermined amount of cam movement, a rack and pinion mechanism for moving the second switch toward and from the cam to vary the said predetermined amount of cam movement prior to the opening Of the switch, a rotatable shaft carrying the pinion and also having a second pinion thereon, a second shaft parallel with the first shaft and movable rotatively and longitudinally, the said second shaft having a pinion meshing with the second pinion on the first shaft whereby the second shaft upon rotation will move the switch, and mechanism connecting the second shaft with the reversing switch whereby the second shaft upon longitudinal movement will operate the reversing switch.

14. The combination in a grinding machine, of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a reversing switch for the motor, a control circuit for the motor having a switch therein which is open during the major portion of the table movement, means operated by the table for closing the switch shortly before the end of table movement in one direction to thereby start the motor, a second normally closed switch in the said control circuit, a cam movable in unison with the having a switch therein which is open duringfeed mechanism for opening the second switch to stop the feed motor after a predetermined amount of cam movement, a rack and pinion mechanism for moving the second switch toward and from the cam to vary the said predetermined amount of cam movement prior to the opening of the switch, a rotatable shaft carrying the pinion and also having a second pinion thereon, a second shaft parallel with the first shaft and movable rotatively and longitudinally, the said second shaft having a pinion meshing with the second pinion on the first shaft whereby the second shaft upon rotation will move the switch, a collar surrounding the second shaft and rotatable therewith but held against longitudinal movement, the said collar being manually rotat able to rotate the shaft, and mechanism connecting the second shaft with the reversing switch whereby the second shaft upon longitudinal movement will operate the reversing switch.

15. In a grinding machine of the class described, the combination of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a control circuit for the motor having openable and closable switch means therein which is mounted for bodily adjustment, means for closing the said switch means near the end of table movement in each direction at a point in the cycle of the machine varied in accordance with the adjusted position of said switch, a switch in the circuit operated by the table so as to occupy two separate closed positions when the table is near the ends of its travel in the respective directions, a switch in the circuit manually operable to connect the switch means with the said table operated switch when the latter is in either of its two closed positions whereby the feed motor is started near one end of the table travel or near the other end thereof, and means for opening the said switch means after a predetermined amount of feeding.

16. In a grinding machine of the class described, the combination of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a control circuit for the motor having openable and closable switch means therein, means for closing the said switch means near the end of table movement in each direction, a switch in the circuit operated by thetable so as to occupy two separate closed positions when the table is near the ends of its travel in the respective directions, a switch in the circuit manually operable to connect the switch means with the said table operated switch when the latter is in either of its two closed positions whereby the feed motor is started near one end of the table travel or near the other end thereof, the last said switch being also manually operable to connect the switch means with the last said table operated switch when it is in both of its two closed positions whereby the feed motor is started near each end of the table travel, and means for opening the said switch means after a predetermined amount of feeding.

17. In a grinding machine of the class described, the combination of a work table, power operated mechanism for reciprocating the table, a cross feed slide carrying the table, a feed motor and connected mechanism for causing feeding of the slide, a control circuit for the motor 17 the major portion of the table movement, means for closing the first switch near the end of table movement in each direction and for opening the said switch after a short predetermined interval, a switch in the circuit operated by the table so as to occupy two separate closed positions when the table is near the ends of its travel in the respective directions, a third switch in the circuitv manually operable to connect the first said switch with the second said switch when the latter is in either of its two closed positions whereby the feed motor is started near one end of the table travel or near the other end thereof, a fourth normally closed switch in the circuit, and means operated by movement of the feed mechanism for opening the fourth said switch after a predetermined amount of feeding to stop the feed motor while the first switch remains closed.

STEPHEN E. WOODBURY.

REFERENCES CITED The following references are of record in the file of this patent:

Huxford et al Nov. 12, 1935 

